Thermoplastic molding compounds based on ethylene polymers and thermoplastic polyesters

ABSTRACT

Thermoplastic molding materials contain, as essential components, 
     A) from 95 to 99.99% by weight of an ethylene polymer and 
     B) from 0.01 to 5% by weight of a thermoplastic polyester having a maximum melting point of less than or equal to 150° C.

The present invention relates to thermoplastic molding materialscontaining, as essential components,

A) from 95 to 99.99% by weight of an ethylene polymer and

B) from 0.01 to 5% by weight of a thermoplastic polyester having amaximum melting point of less than or equal to 150° C.

The present invention furthermore relates to processes for thepreparation of these thermoplastic molding materials, their use for theproduction of fibers, films and moldings, and the fibers, films andmoldings obtainable thereby and comprising the thermoplastic moldingmaterials.

It is known that the processability of ethylene polymers can be improvedby admixing small amounts of fluorine-containing polymers, such aspolyvinylidene fluorides. However, the disadvantage here is thatfluorine is contained in the end product and the fluorine elastomers arepresent as particles in the finished article and cause problems, forexample during printing.

It is an object of the present invention to provide thermoplasticmolding materials which are based on ethylene polymers, do not have thestated disadvantages and exhibit good processability and good surfaceproperties.

We have found that this object is achieved by the thermoplastic moldingmaterials defined at the outset.

We have also found processes for their preparation, their use for theproduction of fibers, films and moldings, and the fibers, films andmoldings obtainable thereby.

The novel thermoplastic molding materials contain, as component A), from95 to 99.99, preferably from 97 to 99.95, in particular from 99 to 99.9,% by weight of an ethylene polymer. This is understood as meaninghomopolymers or copolymers of ethylene, preferably used comonomers beingpropylene, butenes, pentenes, including 4-methylpent-1-ene, and hexenes.However, higher alkenes, in particular alk-1-enes, such as oct-1-ene,may also be used as monomers for copolymers. Blends of differentethylene polymers may also be used. A part of the blends may alsoconsist of polyolefins having polar comonomers and obtained by freeradical polymerization.

There are virtually no restrictions with regard to the density of theethylene polymers; it may vary within wide ranges, for example from0.860 to 0.970 g/cm³. Particularly preferred ethylene polymers are thosewhich have a very low density (ULDPE), which is generally from 0.880 to0.910 g/cm³, those having a low density (LDPE), which is generally from0.910 to 0.935 g/cm³, and those having a medium to relatively highdensity.

The molecular weight distribution (M_(w) /M_(n)) of the ethylenepolymers used may also vary within wide ranges, for example from lessthan 2 to more than 30, an M_(w) /M_(n) of less than 16 being preferred.

The melt flow rates (MFR) of the ethylene polymers used may also varywithin wide ranges, for example from less than 0.01 to 80 g/10 min(190/2.16).

Furthermore, there are virtually no restrictions with regard to theprocesses for the preparation of the ethylene polymers, preparationpreferably being effected using Ziegler, Phillips or metallocenecatalyst systems.

The novel thermoplastic molding materials contain, as component B), from0.01 to 5, preferably from 0.05 to 3, in particular from 0.1 to 1, % byweight of a thermoplastic polyester having a maximum melting point ofless than or equal to 150° C.

Preferred components B) are polyesters which are obtainable by reactinga mixture containing, as essential components,

B1) from 30 to 60, preferably from 32 to 55, % by weight of a mixturecontaining, as essential components,

B11) from 30 to 70, preferably from 35 to 60, % by weight of adipic acidor ester-forming derivatives thereof, in particular di-C₁ -C₆ -alkylesters, such as dimethyl, diethyl, dipropyl, dibutyl, dipentyl ordihexyl adipate, or a mixture thereof, preferably adipic acid ordimethyl adipate or a mixture thereof,

B12) from 30 to 70, preferably from 35 to 60, % by weight ofterephthalic acid or ester-forming derivatives thereof, in particulardi-C₁ -C₆ -alkyl esters, such as dimethyl, diethyl, dipropyl, dibutyl,dipentyl or dihexyl terephthalate or a mixture thereof, preferablyterephthalic acid or dimethyl terephthalate or a mixture thereof,

and

B13) from 0 to 5, preferably from 0.01 to 3, % by weight of a compoundhaving at least three, preferably from three to ten, in particular fromthree to six, groups capable of ester formation, preferably hydroxyland/or carboxyl,

B2) from 40 to 70, preferably from 42 to 65, % by weight of a dihydroxycompound of 2 to 10 carbon atoms, preferably C₂ -C₆ -alkanediols or C₅-C₁₀ -cycloalkanediols or a mixture thereof,

and

B3) from 0 to 5, preferably from 0.01 to 3, % by weight ofdiisocyanates, divinyl ethers, 2,2'-bisoxazolines or a mixture thereof.

The percentages by weight of the components B11), B12) and B13) arebased on B1); the percentage by weight is to be understood in such a waythat the sum of the percentages by weight of the components used is 100.

Examples of preferred components B13) are

tartaric acid, citric acid, malic acid;

trimethylolpropane, trimethylolethane;

pentaerythritol;

polyether triols;

glycerol;

trimesic acid;

trimellitic acid, trimellitic anhydride;

pyromellitic acid, pyromellitic dianhydride and

hydroxyisophthalic acid.

Examples of preferred components B2) are ethylene glycol, 1,2-and1,3-propanediol, 1,2- and 1,4-butanediol, 1,5-pentanediol and1,6-hexanediol, in particular ethylene glycol, 1,3-propanediol and1,4-butanediol, cyclopentanediol, 1,4-cyclohexanediol,1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol and mixturesthereof.

Conventional and commercial diisocyanates may be used as diisocyanates(B3)). A diisocyanate which is selected from the group consisting oftolylene 2,4-diisocyanate, tolylene 2,6-diisocyanate, diphenylmethane4,4'- and 2,4'-diisocyanate, naphthylene 1,5-diisocyanate, xylylenediisocyanate, hexamethylene diisocyanate, isophorone diisocyanate andmethylenebis(4-isocyanatocyclohexane) is preferably used, particularlypreferably hexamethylene diisocyanate.

In principle, trifunctional isocyanate compounds which may containisocyanurate and/or biuret groups having a functionality of not lessthan three may also be used, or some of the diisocyanate compounds B3)may be replaced by tri- or polyisocyanates.

All conventional and commercial divinyl ethers may be used as divinylethers (B3)). Divinyl ethers selected from the group consisting of1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether and1,4-cyclohexanedimethanol divinyl ether are preferably used.

Compounds of the formula ##STR1## where R¹ is a single bond, a (CH₂)_(q)-alkylene group, in which q is 2, 3 or 4, or phenylene,

may be used as 2,2'-bisoxazolines (B3)).

It is also possible to use polyesters B) in which a part of thecomponents B11) and/or B12) has been replaced by aminocarboxylic acids,such as glycine, aspartic acid, glutamic acid, alanine, valine, leucineor isoleucine, and oligo- or polymers obtainable therefrom, such asimides of polyaspartic acid or imides of polyglutamic acid, preferablyglycine. Instead of aminocarboxylic acids, polyamides having a molecularweight of not more than 18,000 g/mol, for example polyamide 46,polyamide 66 or polyamide 610, may also be used.

Polyesters B) in which either the amount of B13) is greater than 0% byweight or the amount of B3) is greater than 0% by weight or both theamount of B13) and the amounts of B3) are greater than 0% by weight areparticularly preferred.

The polyesters B) preferably have a maximum melting point of from 40 to150° C., particularly preferably from 60 to 140° C., in particular from80 to 130° C.

The number average molecular weights M_(n) of the polyesters B) may befrom 2,000 to 100,000, preferably from 4,000 to 80,000, in particularfrom 5,000 to 50,000.

Processes for the preparation of the polyesters B) are not critical perse. All components may be reacted together or some of the components maybe premixed. Basic processes are described, for example, inKunststoff-Handbuch, Volume 3/1 (1992), pages 15 to 23, Carl HanserVerlag, Munich.

For example, the reaction of dimethyl esters of component B1) withcomponent B2) (transesterification) can be carried out at from 160 to230° C. in the melt at atmospheric pressure, advantageously under aninert gas atmosphere.

In the preparation of the polyesters B), a molar excess, based on thecomponent B1), of component B2) is advantageously used, for example upto 2 1/2 times, preferably up to 1.67 times.

The preparation of the polyesters B) is usually carried out with theaddition of suitable catalysts known per se, such as metal compoundsbased on elements such as Ti, Ge, Zn, Fe, Mn, Co, Zr, V, Ir, La, Ce, Liand Ca, preferably organometallic compounds based on these metals, suchas salts of organic acids, alkoxides, acetylacetonates and the like,particularly preferably based on zinc, tin and titanium.

When dicarboxylic acids or anhydrides thereof are used as component B1),their esterification with component B2) can take place before,simultaneously with or after transesterification. In a preferredembodiment, the process for the preparation of modified polyalkyleneterephthalates, which is described in DE-A 23 26 026, is used.

After the reaction of the components B1) and B2), the polycondensationto the desired molecular weight is carried out as a rule under reducedpressure or in an inert gas stream, for example comprising nitrogen,with further heating to 180-260° C., and component B3) is added.

In order to avoid undesirable degradation and/or secondary reactions,stabilizers may also be added, if desired, in this process stage. Suchstabilizers are, for example, the phosphorus compounds described in EP-A13 461 or U.S. Pat. No. 4,328,049 or in B. Fortunato et al., Polymer,Vol. 35, No. 18, pages 4006 to 4010, 1994, Butterworth-Heinemann Ltd.Some of these may also act as deactivators of the catalysts describedabove. Examples are organophosphites, phosphonous acid and phosphorusacid. Examples of compounds which act only as stabilizers are trialkylphosphites, triphenyl phosphite, trialkyl phosphates, triphenylphosphate and tocopherol (vitamin E; for example available as Uvinul®2003AO (BASF)).

The weight ratio of catalyst to polyester B) is usually from 0.01:100 to3:100, preferably from 0.05:100 to 2:100, and smaller amounts, such as0.0001:100, may also be used in the case of highly active titaniumcompounds.

The catalyst may be used directly at the beginning of the reaction, justbefore the excess diol is separated off or, if desired, also dividedinto a plurality of portions during the preparation of the polyestersB). If desired, different catalysts or mixtures thereof may also beused.

A particularly preferred preparation of the polyesters B) is carried outby a procedure in which a prepolymer is first prepared from thecomponent B11) and the component B2), and this prepolymer is thenreacted with the component B12) and further B2) and with the componentB13), and B3) is then added. In the preparation of the prepolymer, waterand the excess of B2) and, for example, methanol are preferablydistilled off.

The preparation of the novel thermoplastic molding materials is notcritical per se. Preferably, the two components A) and B) are mixed atfrom 100 to 350° C, in particular from 150 to 260° C.

The novel thermoplastic molding materials are suitable for theproduction of fibers, films and moldings, in particular of films,profiles and hollow articles. They have in particular goodprocessability and good surface properties.

EXAMPLES

The following components were used:

PE1: An ethylene copolymer containing 7% by weight of but-1-ene andhaving a molecular weight distribution M_(w) /M_(n) of 4 (M_(w) weightaverage, M_(n) number average), a melt flow rate MFR (190/2.16) of 1g/10 min and a density of 0.920 g/cm³.

PE2: An ethylene copolymer containing 10% by weight of but-1-ene andhaving a molecular weight distribution of 2, a melt flow rate of 1.8g/10 min and a density of 0.902 g/cm³.

PE3: An ethylene copolymer containing 1.5% by weight of hex-1-ene andhaving a molecular weight distribution of 15, a melt flow rate 190/21,6of 6 g/10 min and a density of 0.946 g/cm³.

B: A polyester which was prepared as follows:

Prepolymer

4,672 kg of 1,4-butanediol, 7,000 kg of adipic acid and 50 g of tindioctoate were heated to 240° C. under a nitrogen atmosphere. After theprinciple amount of the water formed in the reaction had been distilledoff, 10 g of titanium tetrabutylate were added. After the acid number ANhad reached a value of less than 1, the excess butanediol was distilledoff under reduced pressure until an OH number of 56 had been reached.

1.81 kg of this prepolymer, 1.17 kg of dimethyl terephthalate, 1.7 kg of1,4-butanediol and 4.7 g of titanium tetrabutylate were heated to 180°C. under a nitrogen atmosphere while stirring. The methanol formed inthe transesterification reaction was distilled off.

The mixture was heated to 230° C. in the course of 2 hours whileincreasing the stirring speed, 6.54 g of pyromellitic dianhydride wereadded and, after a further hour, another 0.4 g of 50% strength aqueousphosphorous acid was introduced. At the end of the reaction, the meltwas cooled to 200° C. under a nitrogen atmosphere while stirring. 15 gof hexamethylene diisocyanate were then added in 4 portions in thecourse of 40 minutes. The resulting polyester could be granulated.

    ______________________________________                                        OH number =      2        mg KOH/g                                              AN = 5.5 mg KOH/g                                                             M.sub.n  = 14,320                                                             M.sub.w  = 98,350 (GPC)                                                       Melting point T.sub.m  = 98° C.                                        Glass transition temperature Tg = -31° C. (DSC, cooled rapidly                                    from 190° C.)                             ______________________________________                                    

EXAMPLES 1 to 12

Production of Films

PE1 and PE2 were mixed with different amounts of B as a mixture ofgranules at various melt temperatures and were extruded to give blownfilms. A transparent film free of melt fracture was obtained in everycase.

Comparative Examples V1 to V5

The procedure was similar to that of Examples 1 to 12, but without theaddition of the polyester B.

A film exhibiting pronounced melt fracture was obtained in every case.

The test parameters and the materials used are listed in Table 1.

                                      TABLE 1                                     __________________________________________________________________________                            Melt  Die                                                  temperature diameter Die gap Output                                        Example Component A) Component B) [° C.] [mm] [mm] [kg/h]            __________________________________________________________________________     1   99.0% by weight of PE1                                                                    1.0% by weight                                                                       200    50  0.8  3                                        2 99.0% by weight of PE1 1.0% by weight 200  50 0.8  8                        3 99.5% by weight of PE1 0.5% by weight 200  50 0.8  3                        4 99.5% by weight of PE1 0.5% by weight 200  50 0.8  8                        5 99.7% by weight of PE1 0.3% by weight 200  50 0.8  3                        6 99.7% by weight of PE1 0.3% by weight 200  50 0.8  8                        7 99.0% by weight of PE2 1.0% by weight 180 150 1 25                          8 99.0% by weight of PE2 1.0% by weight 200 150 1 25                          9 99.0% by weight of PE2 1.0% by weight 225 150 1 25                         10 99.0% by weight of PE2 1.0% by weight 180 150 1 80                         11 99.0% by weight of PE2 0.5% by weight 200 150 1  80*                       12 99.0% by weight of PE2 1.0% by weight 225 150 1 80                         V1 100.0% by weight of PE1  -- 200  50 0.8  3                                 V2 100.0% by weight of PE2  -- 180 150 1 25                                   V3 100.0% by weight of PE2  -- 200 150 1 25                                   V4 100.0% by weight of PE2  -- 225 150 1 25                                   V5 100.0% by weight of PE2  -- 200 150 1 80                                 __________________________________________________________________________     *The pressure in the processing machine decreased from 480 bar to 350 bar     (compared with V5)                                                       

EXAMPLE 13

Production of Bottles

99% by weight of PE3 together with 1% by weight of B as a mixture ofgranules were blow-molded to 300 ml bottles at a melt temperature of200° C. The melt pressure decreased from 120 bar to 105 bar comparedwith a bottle comprising 100% by weight of PE3.

The bottles exhibited better surface gloss, and the stress crackresistance test indicated a 20% longer life than bottles comprising 100%by weight of PE3.

EXAMPLE 14

Production of Extruded Films

99.5% by weight of PE2 were extruded with 0.5% by weight of B at a melttemperature of 260° C. on a flat film extrusion line having a slot dieof 900 mm. No melt fracture occurred even at an output of 100 kg/h,whereas a film comprising 100% by weight of PE exhibited pronounced meltfracture at an output as low as 30 kg/h.

We claim:
 1. A thermoplastic molding material consisting essentiallyofA) from 95 to 99.99% by weight of an ethylene polymer and B) from 0.01to 5% by weight of a thermoplastic polyester having a melting point ofless than or equal to 150° C., wherein the thermoplastic polyester B) isobtained by reacting a composition consisting essentially ofB₁) from 30to 60% by weight of a mixture consisting essentially ofB₁₁) from 30 to70% by weight of adipic acid, the ester-forming derivatives thereof or amixture thereof, B₁₂) from 30 to 70% by weight of terephthalic acid, theester-forming derivatives thereof or a mixture thereof and B₁₃) from 0to 5% by weight of a compound having at least three groups capable ofester formation, B₂) from 40 to 70% by weight of a dihydroxy compound of2 to 10 carbon atoms and B₃) from 0 to 5% by weight of isocyanates,divinyl ethers, 2,2'-bisoxazolines or a mixture thereof, saidthermoplastic polyester comprising polymer units formed from componentB₁₃) or polymer units formed from component B₃).
 2. The thermoplasticmolding material defined in claim 1, wherein the thermoplastic polyestercomprises polymer units formed from component B₁₃) and polymer unitsformed from component B₃).
 3. The thermoplastic molding material definedin claim 1, wherein B₃) is present in from 0.01 to 3% by weight, basedon the amount of B).
 4. The thermoplastic molding material defined inclaim 1, wherein B₁₃) is present in from 0.01 to 3% by weight, based onthe amount of B₁).
 5. The thermoplastic molding material defined inclaim 4, wherein B₁₃) is a compound having from 3 to 10 groups capableof ester formation.
 6. The thermoplastic molding material defined inclaim 4, wherein B₁₃) is selected from the group consisting of tartaricacid, citric acid, malic acid, trimethylolpropane, trimethylolethane,pentaerythritol, polyether triols, glycerol, trimesic acid, trimelliticacid, trimellitic acid anhydride, pyromellitic acid, pyromelliticdianhydride, hydroxyisophthalic acid and mixtures of two or morethereof.
 7. A fiber, film or molding comprising the thermoplasticmolding material defined in claim
 1. 8. A fiber, film or moldingconsisting essentially of the thermoplastic molding material defined inclaim
 1. 9. A method of improving the processability of an ethylenepolymer without adverse effects on the surface properties, which methodcomprises blending the polyethylene polymer with a thermoplasticpolyester in a weight ratio of polyethylene polymer to thermoplasticpolyester of from 95:5 to 99.99:0.01 at a temperature of from 100 to350° C.,wherein the thermoplastic polyester has a melting point of lessthan or equal to 150° C. and is obtained by reacting a compositionconsisting essentially ofB₁) from 30 to 60% by weight of a mixtureconsisting essentially ofB₁₁) from 30 to 70% by weight of adipic acid,the ester-forming derivatives thereof or a mixture thereof, B₁₂) from 30to 70% by weight of terephthalic acid, the ester-forming derivativesthereof or a mixture thereof and B₁₃) from 0 to 5% by weight of acompound having at least three groups capable of ester formation, B₂)from 40 to 70% by weight of a dihydroxy compound of 2 to 10 carbon atomsand B₃) from 0 to 5% by weight of isocyanates, divinyl ethers,2,2'-bisoxazolines or a mixture thereof, and wherein said thermoplasticpolyester comprises polymer units formed from component B₁₃) or polymerunits formed from component B₃).
 10. The method of claim 9, wherein thethermoplastic polyester comprises polymer units formed from componentB₁₃) and polymer units formed from component B₃).
 11. The method ofclaim 9, wherein B₃) is present in from 0.01 to 3% by weight, based onthe amount of B).
 12. The method of claim 9, wherein B₁₃) is present infrom 0.01 to 3% by weight, based on the amount of B₁).
 13. The method ofclaim 12, wherein B₁₃) is a compound having from 3 to 10 groups capableof ester formation.
 14. The method of claim 12, wherein B₁₃) is selectedfrom the group consisting of tartaric acid, citric acid, malic acid,trimethylolpropane, trimethylolethane, pentaerythritol, polyethertriols, glycerol, trimesic acid, trimellitic acid, trimellitic acidanhydride, pyromellitic acid, pyromellitic dianhydride,hydroxyisophthalic acid and mixtures of two or more thereof.